Effect Menu

From Audacity Development Manual

Peter 29Apr15:ToDo-2P Placeholder to remind us that if the list of effects changes we also need to update the image on the Edit Chains page.

Audacity includes many built-in effects and also lets you use a wide range of plug-in effects. You can download many free plug-ins for Audacity from our website. Plug-ins always appear underneath the divider in the Effect menu. Released builds of Audacity include sample Nyquist and/or LADSPA effects.

To apply an effect, select part or all of the track(s) you want to modify, and select the effect from the menu. Titles which end in an ellipsis (...) will bring up a dialog asking you for more parameters.

All effects that have a dialog let you hear the audio as modified by the effect before you apply the effect to the waveform.

All other effect types supported in Audacity (LADSPA, LV2, VST and Audio Units for Mac) support real-time preview - you can change the effect settings while listening then press Apply to apply the effect to the waveform.

When playing, recording or paused, effects in the Effect menu that do not support real-time preview will appear grayed out. Press the yellow Stop button to access these types of effect.

For quick access to an effect, you can use CTRL + R to repeat the last used effect at the same settings, and you can use Keyboard Preferences to set up keyboard shortcuts for effects that you use often.

Where a built-in or shipped Nyquist effect has an interface, its description page (accessed by the links below) shows an image of the interface and its default settings.

Manage...

Selecting this option from the Effect Menu (or the Generate Menu or Analyze Menu) takes you to a dialog which enables you to load and unload Effects (and Generators and Analyzers) from Audacity. This enables you to customize your Effect Menu making it shorter or longer as required. For details see Manage Effects, Generators and Analyzers.

By default all the Built-in effects, with the exception of Classic Filters, are loaded in Audacity.

Built-in effects

Audacity's built-in effects (those that appear in the program irrespective of the contents of your Audacity and other "Plug-Ins" folders) are above the divider in the Effect menu.

Most of the built-in effects (and most Nyquist effect plug-ins shipped with Audacity) have a Preview button. This allows you to listen to how the first six seconds (by default) of the selected audio would sound if you pressed OK to apply the effect. The preview length can be changed on the Playback tab of Preferences.

All selected tracks are previewed irrespective of whether the tracks are muted or soloed. This is because the effect is applied to the selected audio. If Preview does not sound quite as you want, adjust the controls of the effect and Preview again.

Built-in effects support saving of user presets but do not yet support real-time preview or import/export of presets from/to other machines.

Increases or decreases the volume of the audio you have selected. When you open the dialog, Audacity automatically calculates the maximum amount you could amplify the selected audio without causing clipping (distortion caused by trying to make the audio too loud).

Reduces (ducks) the volume of one or more tracks whenever the volume of a specified "control" track reaches a particular level. Typically used to make a music track softer whenever speech in a commentary track is heard.

Click Removal is designed to remove clicks on audio tracks and is especially suited to declicking recordings made from vinyl records. It will usually work best on very short clicks. For broader individual pops in selections up to 128 samples wide (about three milliseconds at 44100 Hz project rate), you could try the Repair effect.

Compresses the dynamic range by two alternative methods. The default "RMS" method makes the louder parts softer, but leaves the quieter audio alone. The alternative "peaks" method makes the entire audio louder, but amplifies the louder parts less than the quieter parts. Make-up gain can be applied to either method, making the result as loud as possible without clipping, but not changing the dynamic range further.

Repeats the selected audio again and again, normally softer each time. The delay time between each repeat is fixed, with no pause in between each repeat. For a more configurable echo effect with a variable delay time and pitch-changed echoes, see Delay...

Applies a fade-in to the selected audio, so that the amplitude changes gradually from silence at the start of the selection to the original amplitude at the end of the selection. The shape of the fade is linear. The rapidity of the fade-in depends entirely on the length of the selection it is applied to.

Applies a fade-out to the selected audio, so that the amplitude changes gradually from the original amplitude at the start of the selection down to silence at the end of the selection. The shape of the fade is linear. The rapidity of the fade-out depends entirely on the length of the selection it is applied to.

Leveler is a simple, combined compressor and limiter effect for reducing the dynamic range of audio. It reduces the difference between loud and soft, making the audio easier to hear in noisy environments or on small loudspeakers. It is best suited to speech recordings but at heavier settings or used multiple times it can also be used as a simple distortion effect for voices or instruments.

Use Paulstretch only for an extreme time-stretch or "stasis" effect. This may be useful for synthesizer pad sounds, identifying performance glitches or just creating interesting aural textures. Use Change Tempo or Sliding Time Scale rather than Paulstretch for tasks like slowing down a song to a "practice" tempo.

The name "Phaser" comes from "Phase Shifter", because it works by combining phase-shifted signals with the original signal. The movement of the phase-shifted signals is controlled using a Low Frequency Oscillator (LFO).

Rapid tone quality variations, like that guitar sound so popular in the 1970's.

Wahwah uses a moving bandpass filter to create its sound. A low frequency oscillator (LFO) is used to control the movement of the filter throughout the frequency spectrum.

The phase of the left and right channels is automatically adjusted when given a stereo track, so that the effect seems to travel across the speakers.

Nyquist effects

Not a priority for 2.1, but needs a little more here:

where to get docs

the debug button in Nyquist effects

Peter 17Jun15: Both done, removed the Px

Nyquist effects support saving of user presets but do not yet support real-time preview or import/export of presets from/to other machines.

Nyquist plug-ins provide most of the optional effects underneath the divider in the Effect menu. They are also used to provide some of Audacity's built-in audio generators and analysis tools. A wide range of additional Nyquist effect, generation and analysis plug-ins can be obtained from Download Nyquist Plug-ins on our Wiki.

The Debug button in most Nyquist effect dialogs opens a "Nyquist Output" window containing any informational or error output provided by the effect. This is primarily of use when writing or editing Nyquist plug-ins. After pressing OK in this window, the effect or other chosen action is attempted just as it would be if pressing OK in the effect instead of using the Debug button.

To add a new Nyquist plug-in, put it in the Audacity "Plug-Ins" folder.

On Windows and OS X the "Plug-Ins" folder is in the directory where Audacity resides - usually C:\Program Files or C:\Program Files (x86) on Windows or the "Applications" folder on OS X.

On Linux, the "plug-ins" folder is in usr/share/audacity if you installed an Audacity package supplied by your distribution, or usr/local/share/audacity if you compiled Audacity from source code. Optionally a "plug-ins" folder can be created in the home directory thus: ~/.audacity-files/plug-ins (you can also call the folder "plugins").

Some Nyquist plug-ins could crash while processing very long audio selections (typically an hour or more). This is due to the plug-in using a large amount of memory and is a known issue in Audacity's current Nyquist implementation. Try using the plug-in on shorter selections instead.

Nyquist Workbench

For advanced users who can compile Audacity, Nyquist Workbench gives the ability to run arbitrary Nyquist code in Audacity from a graphical IDE (Integrated Development Environment). See Nyquist Workbench in the Wiki for details.

Nyquist plug-ins included in Audacity

The following sample Nyquist plug-ins are included in released builds of Audacity:

Launches a dialog box where you can choose the shape of the fade in or fade out to be applied. You can also create fades to and from other than silence or full volume. An example of this might be a fade in from 20% of the original volume to 80% of the original volume.

Limiter passes signals below a specified input level unaffected or gently reduced, while preventing the peaks of stronger signals from exceeding this threshold. Limiting is a type of dynamic range compression. Mastering engineers often use limiting combined with make-up gain to increase the perceived loudness of an audio recording during the audio mastering process.

Peter 01Aug15:ToDo-1 will need updating as Paul has removed the special Spectral Selection views.

Spectral edit multi tool (and Spectral edit parametric EQ and Spectral edit shelves described immediately following) are intended for working on a combined frequency and time selection made when using one of the Spectral Selection views.

If a fully defined spectral selection has been made, the effect applies a low shelf filter, high shelf filter or combined low and high shelf filter according to the value you enter in the "Gain (dB)" control. See Spectral edit shelves for more information.

Attempts to remove or isolate center-panned audio from a stereo track. Vocals are often (but not always) recorded in this way. The classic method achieves this by subtracting one channel from the other, but the result will be (dual) mono (this method can be found under the Actions menu in this effect as "Remove Center Classic (Mono)" and is a quick way to remove the center if only mono is needed). All other "Remove" options in this effect preserve the stereo image

Attempts to remove center-panned audio from a stereo track. Vocals are often (but not always) recorded in this way. Vocals (or other audio) can only be removed with this plug-in when panned to center, in other words sounding equally loud in both left and right channels. Help text is available from within the effect's dialog box. This is a "Legacy effect": the same result can be achieved by using the Remove Center Classic (Mono) option in Vocal Reduction and Isolation.

Vocoder synthesizes a modulator (usually a voice) in the left channel of a stereo track with a carrier wave in the right channel to produce a modified version of the left channel. Vocoding a normal voice with white noise as provided in the effect will produce a robot-like voice for special effects. Other carriers can be used for subtly different voices. Vocoder can only be applied to unsplit stereo tracks.

LADSPA effects

Peter 30Jun13: All the LADSPA effects still carry author attribution.

Gale 06Jul13: It's been decided that there is no "simple" solution to this - the plug-in code can easily be hacked to remove the credits and license but then to strictly satisfy GPL we'd have to store the modified source code (as well as add attribution for one author). Probably both these effects will ultimately be replaced with ones written by "us".

LADSPA (Linux Audio Developer's Simple Plug-in API) plug-ins were originally developed for the Linux platform, but ports of some plug-ins are available for Windows and OS X as well. Most LADSPA plug-ins are effects, but they are also used to provide some of Audacity's built-in audio generators and can be used for audio analysis. Additional LADSPA plug-ins can be downloaded for Windows, Mac and Linux.

LADSPA effects support real-time preview. They do not support import/export of presets but do support saving presets for use in Audacity only. A few LADSPA plug-ins have an "Effect Output" section which is populated after the effect is applied.

LADSPA plug-ins shipped with Audacity

A stereo compressor with a variable envelope follower for RMS / peak behavior.

Adding a LADSPA plug-in

To add a LADSPA plug-in, put it in the Audacity "Plug-ins" folder:

On Windows and OS X the "Plug-ins" folder is in the directory where Audacity resides - usually C:\Program Files or C:\Program Files (x86) on Windows or the "Applications" folder on OS X.

On Linux, the "plug-ins" folder is in usr/share/audacity if you installed an Audacity package supplied by your distribution, or usr/local/share/audacity if you compiled Audacity from source code. Optionally a plug-ins folder can be created in the home directory ~/.audacity-files/plug-ins.

Then use Effect > Manage... to enable the LADSPA effects and load them into Audacity, For details see Manage Effects.

Audacity will also load LADSPA plug-ins from the following system locations:

All operating systems: The path specified by the LADSPA_PATH environment variable

additionally on OS X:

~/Library/Audio/Plug-Ins/LADSPA

/Library/Audio/Plug-Ins/LADSPA

additionally on Linux/Unix:

~/.ladspa

/usr/local/lib/ladspa

/usr/lib/ladspa

$LIBDIR/ladspa

Saving LADPSA effect settings as a User Preset

To save the current effect settings as a User Preset, select Save As... from the Manage menu in the effect dialog which brings up the following dialog:

Type a name for the preset then click OK after which the saved preset will appear in the "User Presets" list in the Manage menu.

LADSPA Effect Options

In the effect's dialog, click the Manage button then choose Options... to bring up the dialog illustrated below. When you change the options in this dialog, the changes apply only to the current effect that's open. All other LADSPA effects will remain at the default options shown below until you change their options.

Latency Compensation: This setting (enabled by default) compensates for waveform delay caused by LADSPA effects which preload audio data to a buffer. Compensation may not work in all cases, and for it to work, any compensation or latency reporting settings in the effect itself must be enabled. If compensation fails or if this Audacity setting is unchecked, effects that buffer audio will insert silence at the start of the processed selection and remove a corresponding amount of audio from the end of the selection. Enabling or disabling compensation is effective immediately.

Effects of the following LV2, VST and Audio Unit (Mac only) classes are always third-party plug-ins added by the user (and also by the operating system in case of Audio Units).

LV2 effects

LV2 effects support real-time preview. They do not support import/export of presets but do support saving presets for use in Audacity only.

Most LV2 effects that have a graphical interface will show that interface by default in Audacity. Some LV2 effects do not allow directly embedding their interface into our effect dialog, so those effects will only show a textual interface in Audacity.

Some LV2 effects require features that are not yet supported in Audacity, so display an error message when applying the effect.

LV2 is a more advanced evolution of the LADSPA plug-in architecture. Note that LV2 effects in Audacity cannot yet display a full graphical interface.

To add a new LV2 effect, place its complete ".lv2" folder (not the files alone) at the top level of any of the following searched for locations, then use Effect > Manage... to enable the LV2 effects and load them into Audacity, For details see Manage Effects.

$HOME/.lv2:/usr/local/lib/lv2:/usr/lib/lv2 (assuming $PREFIX is /usr/local as it should be by default)

LV2 Effect Options

In the effect's dialog, click the Manage button then choose Options... to bring up the dialog illustrated below. When you change the options in this dialog, the changes apply only to the current effect that's open. All other effects will remain at the default options shown below until you change their options.

Latency Compensation: This setting (enabled by default) compensates for waveform delay caused by effects which preload audio data to a buffer. Compensation may not work in all cases, and for it to work, any compensation or latency reporting settings in the effect itself must be enabled. If compensation fails or if this Audacity setting is unchecked, effects that buffer audio will insert silence at the start of the processed selection and remove a corresponding amount of audio from the end of the selection. Therefore leave this option checked unless a particular effect does not work even after reducing the buffer size, in which case you can experiment by unchecking this option. Enabling or disabling compensation is effective immediately.

Graphical Mode: This setting (enabled by default) allows some effects to display a graphical (instead of a plain text) interface. If you change this setting you must close the settings dialog, then close and reopen the effect to see the change.

VST effects

VST effects support import/export of presets (where the particular effect supports this) and support saving presets for use in Audacity only.

Adding a new VST effect in Audacity

A wide range of VST effects can be obtained online. VST instruments are not supported. 64-bit VST effects are not supported on Windows or Mac OS X even on 64-bit systems. Conversely on Linux 64-bit systems, only 64-bit VST's are supported.

To add a new VST effect most easily, put its DLL (Windows), VST (Mac) or SO (Linux) file plus any configuration files or folders it requires in the Audacity "Plug-ins" or "plug-ins" folder inside the directory where Audacity resides.

If no VST_PATH environment variable is found, the following are searched:

LIBDIR/vst (where LIBDIR is defined at build time)

/usr/lib/vst

/usr/local/lib/vst

~/.vst.

All the directories where you can place VST plug-ins are searched recursively, which means that plug-ins that are inside their own folder in that directory should still be found by Audacity.

Saving, Exporting and Importing VST Effect Presets

Not all VST effects support importing and exporting of presets. If an exported preset file is empty, the effect probably does not support presets and Audacity will not be able to import the saved presets.

Save As...

To save the current effect settings as a User Preset, select Save As... from the Manage menu in the effect dialog which brings up the following dialog:

Type a name for the preset then click OK after which the saved preset will appear in the "User Presets" list in the Manage menu.

Export...

Presets for VST effects are exported to a file. A presets file lets you move settings for a particular effect between computers on any operating platform that supports that effect.

Select Export... from the Manage menu in the effect dialog to bring up the "Save VST Preset As:" dialog

Be sure to choose a file type in the “Save as type:” dropdown menu (“Format” dropdown menu on Mac)

Type a name for the file in the "File Name" box ("Save As:" box on Mac) then click OK to export the current effect settings to a separate file.

The following file formats are supported:

XML format: The default choice, which saves an Audacity VST preset file. This is the least flexible choice, mainly useful for the small number of effects that don't support FXP presets. Most other VST host applications don't support XML, so you may only be able to share XML presets between other computers running Audacity.

FXP format: Saves a standard VST program file, which is the most portable choice. It allows you to save the currently visible settings. The saved preset can then be loaded by the same effect running in Audacity or most other VST host applications, on any computer or operating platform it supports. Similarly FXP presets saved by a given effect in any VST host on any computer can be loaded into that effect in Audacity.

FXB format: Saves a standard VST bank file, containing the current settings of all the factory presets for the effect. The saved "bank" of factory presets at your favorite settings can then be loaded by the same effect running in Audacity or any other VST host application supporting FXB presets, on any computer or operating platform it supports. Similarly an FXB bank saved by a given effect in any VST host on any computer can be loaded into that effect in Audacity.

By default presets are saved to the same location as the audacity.cfg file, but you can choose to save them anywhere. Since there is no distinction between preset files saved by different effects you may want to create a folder for each effect you save presets for, or include the effect name in the file name.

Gale 08Feb15:ToDo-2P The below tip does not seem to be true on Windows or the tip is ambiguous. "File name:" box is empty when exporting, even if a factory preset was loaded.

Peter 10Feb15: I agree, this advice note makes no sense to me either. Accordingly I have commented it out, removed the P1 - but left a P2 as a placeholder.

Gale 10Feb15: Same on Mac and Linux - the file name box in the export dialog is empty. Nor does the XML file itself contain the preset name in its text. I "think" what is being said is that the FXP and FXB files contain the internal preset name(s) and that these internal names "may" show in the VST effect itself if the effect supports a separate list of presets in its own GUI. I can't find a way yet to get duplicate internal names in Manage menu > Factory Presets. I agree this may be a good tip but it is too confusing to publish it at the moment.

Tip when exporting VST presets

The exported VST preset file will contain the name of the preset. If you started with a named User or Factory Preset you may want to Save the settings with a unique name as a User Preset. This way, when you or someone else Imports the preset file they will not have duplicate preset names.

On Mac OS X and Linux please take note:

Gale 10Aug14:ToDo-2P Placeholder to watch this and remove this note if the bug is fixed.

the XML, FXP or FXB file extension is not automatically added by Audacity - be sure to include it in the file name (for example, "myPreset.fxp")

make sure the file extension you add is the same as that shown in the "File Format" dropdown menu, otherwise the preset cannot be loaded.

Import...

Select Import... from the Manage menu in the effect dialog to bring up the "Load VST Preset:" dialog

Navigate to the place where you exported a VST preset file.

Click the open button to load the settings.

Depending on how the particular VST effect handles importing presets, the imported preset may show up in the User Presets submenu, the Factory Presets submenu or may not show up at all.

VST Effect Options

In the effect's dialog, click the Manage button then choose Options... to bring up the dialog illustrated below. When you change the options in this dialog, the changes apply only to the current effect that's open. All other VST effects will remain at the default options shown below until you change their options.

Buffer Size: Controls the number of samples sent to the effect in each round of processing. The default buffer size of 8192 should be safe for all VST effects. You can set a higher value which will allow faster processing but some effects may not work at higher values. Changing the buffer size is effective immediately.

Latency Compensation: This setting (enabled by default) compensates for waveform delay caused by VST effects which preload audio data to a buffer. Compensation may not work in all cases, and for it to work, any compensation or latency reporting settings in the effect itself must be enabled. If compensation fails or if this Audacity setting is unchecked, effects that buffer audio will insert silence at the start of the processed selection and remove a corresponding amount of audio from the end of the selection. Therefore leave this option checked unless a particular VST does not work even after reducing the buffer size, in which case you can experiment by unchecking this option. Enabling or disabling compensation is effective immediately.

Graphical Mode: This setting (enabled by default) allows most VST effects to display a graphical (instead of a plain text) interface. If you change this setting you must close the settings dialog, then close and reopen the effect to see the change.

Audio Unit effects

Gale 16Feb15: P1 Import/export of AU presets has major issues, meaning that the Manual will have to attempt to describe the issues and should probably say not to use import/export. Leland, Bill and I are discussing it.

Gale 22Feb15: Documented the weirdness as far as Bill and I understand it, removed the P1.

Audio Unit effects support import/export of presets (see the description below of how it works) and support saving presets for use in Audacity only.

Adding Audio Unit effects

To add a new Audio Unit effect, place it in either of the following system plug-in directories:

~/Library/Audio/Plug-Ins/Components (user plug-ins)

/Library/Audio/Plug-Ins/Components (system-wide plug-ins)

Then use Effect > Manage... to enable the Audio Unit effects and load them into Audacity, For details see Manage Effects.

Saving, Exporting and Importing Audio Unit Effect Presets

Save As...

To save the current effect settings as a User Preset, select Save As... from the Manage menu in the effect dialog which brings up the following dialog:

Type a name for the preset then click OK after which the saved preset will appear in the "User Presets" list in the Manage menu.

Export...

Bill 15Jun2015: Export of AU presets now appears to be working properly. I can:

create three user presets,

close the effect

open the effect

load the defaults

export the three named user presets

delete the three named user presets

close the effect

open the effect

import the three named user presets

I can now select any of them from the User Presets menu item and the correct parameters are loaded into the effect.

If this can be confirmed I will re-write this section.

Bill 25Jun2015:ToDo-2R I have re-confirmed the above, and Leland has indicated he's "worked on it", so amending this section to reflect current behaviour.

Before you can export a preset you must already have saved it as a User Preset.

Each preset for Audio Unit effects is exported to a separate ".aupreset " file at /Users/<yourUserName>/Library/Audio/Presets/Apple/<effectName>/. A presets file lets you move settings for a particular effect between computers.

To export a saved User Preset, select Export... from the Manage menu
in the effect dialog which brings up the following dialog:

Select the user preset(s) you want to export then click OK to export each selected preset to a file. If there is only one preset in the list you must still select it, or nothing will be exported.

Import...

Select Import... from the Manage menu in the effect dialog which brings up the following dialog:

Select the preset(s) you want to import then click OK to import each preset file as a User Preset.

Importing one or more presets does not load new settings into the effect. You must select one of the imported presets from User Presets... in the Manage menu
to load its settings into the effect.

Audio Unit Effect Options

In the effect's dialog, click the Manage button then choose Options... to bring up the dialog illustrated below. When you change the options in this dialog, the changes apply only to the current effect that's open. All other Audio Unit effects will remain at the default options shown below until you change their options.

Latency Compensation: This setting (enabled by default) compensates for waveform delay caused by Audio Unit effects which preload audio data to a buffer. Compensation may not work in all cases, and for it to work, any compensation or latency reporting settings in the effect itself must be enabled. If compensation fails or if this Audacity setting is unchecked, effects that buffer audio will insert silence at the start of the processed selection and remove a corresponding amount of audio from the end of the selection. Enabling or disabling compensation is effective immediately.

Graphical Mode: This setting (enabled by default) allows most Audio Unit effects to display a graphical (instead of a plain text) interface. If you change this setting you must close the settings dialog, then close and reopen the effect to see the change.